Pancreatic cancer is the fourth leading cause of cancer death in the U.S. and newly diagnosed patients have a 5-year survival rate of less than 5%. New treatments for patients with metastatic and locally advanced disease are needed. Cetuximab (Erbitux) is a monoclonal antibody (mAb) that recognizes the HER1 tyrosine kinase receptor that is over-expressed in greater than 70% of pancreatic cancers. Although administration of cetuximab to patients with metastatic pancreatic cancer can lead to tumor regression in 15% of cases, the impact of this agent on overall survival has been low. The activity of cetuximab and other therapeutic anti- tumor mAbs is attributed to their direct, anti-proliferative and pro-apoptotic effects on tumor cells. These direct effects of mAbs are reflective of their ability to inhibit constitutive tyrosine kinase receptor signal transduction. However, tumor bound mAbs may also activate innate immune cells that bear receptors (R) for the Fc or "constant" region of immunoglobulin G. Our group has demonstrated in vitro, in murine models, and in phase I clinical trials that activating cytokines can enhance the anti-tumor activity of mAbs via their ability to stimulate potent natural killer (NK) cell and monocyte cytotoxicity and cytokine secretion. We found that interleukin-21 (IL-21) significantly enhanced NK cell cytotoxic activity against cetuximab-treated pancreatic cancer cells, and stimulated synergistic NK cell production of interferon-? and chemokines that could induce the migration of T cells. IL-21 was also effective in augmenting the anti-tumor effects of cetuximab in a murine xenograft model of HER1+ cancer. We hypothesize that IL-21 administration will enhance the anti-tumor activity of cetuximab against HER1+ pancreatic cancer cells via the activation of innate immune effector cells with activating FcR. IL-21 is well-tolerated, clinically available, and has activity as a single agent. This proposal provides an outline for the preclinical studies that must be performed in order for IL-21 to be employed in the setting of pancreatic cancer in combination with cetuximab. The specific aims of this proposal are: 1). To characterize the NK cell response to cetuximab-coated pancreatic cancer cells following co-stimulation with IL-21, and 2). To examine the mechanism by which IL-21 enhances cetuximab-induce tumor regression in a murine model of HER1-positive cancer and determine if the addition of cytotoxic chemotherapy to the IL-21/cetuximab regimen leads to improved anti-tumor activity. PUBLIC HEALTH RELEVANCE: The program seeks to generate pre-clinical data using in vitro studies with human natural killer cells and a murine tumor model to support the use of interleukin-21 and an anti-HER1 monoclonal antibody (cetuximab) in patients with metastatic or locally advanced pancreatic cancer.